The objective of this study is the understanding of the intertemporal relationships between fertility rates and mortality rates, migration, and variations in economic conditions. Primary attention will be devoted to utilizing long time series of annual data to analyze the variance, covariance, and lag structure of variables representing births, deaths, family formation, percaptita income, savings, interest rates, and technology. Rates from the United States, Sweden, and the United Kingdom will be utilized in this study. These relationships will be analyzed utilizing a dynamic simultaneous equation model which takes account of feedback relationships between economic and demographic variables. The techniques of spectral analysis will be utilized to identify the lag structure and test the statistical significance of relationships.